Pressure Compensated Rotating Electrical Contact

ABSTRACT

A technique facilitates communication of electrical signals in harsh environments and between components that undergo relative rotation with respect to each other. The technique comprises rotatably mounting a first component with respect to a second component. The first component also is electrically coupled with the second component via an electrical coupler. The electrical coupler may comprise a first electrical contact located at the first component and a second electrical contact located at the second component. The first electrical contact is conductively connected with the second electrical contact via a conductive bearing. The conductive bearing is located in a volume which is filled with a substantially incompressible fluid to protect the bearing.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present document is based on and claims priority to U.S. ProvisionalApplication Ser. No.: 62/014,086, filed Jun. 18, 2014, which isincorporated herein by reference in its entirety.

BACKGROUND

In many hydrocarbon well applications, a wellbore is formed in ahydrocarbon-bearing formation and a well string is deployed in thewellbore. The well string is formed with tubing and other types ofdownhole components, some of which are electrically operated or compriseelectrical devices. Sometimes an electrical contact is formed between arotating component and a stationary component via a slip ring to enableelectrical communication with a downhole electrical device. However, thehigh pressures, dirty environments, and shocks that often occur in adownhole environment can have a detrimental impact on the functionalityand longevity of the electrical contact.

SUMMARY

In general, a system and methodology are provided to facilitatecommunication of electrical signals in harsh environments and betweencomponents that undergo relative rotation with respect to each other.The technique comprises rotatably mounting a first component withrespect to a second component. The first component also is electricallycoupled with the second component via an electrical coupler. Theelectrical coupler may comprise a first electrical contact located atthe first component and a second electrical contact located at thesecond component. The first electrical contact is conductively connectedwith the second electrical contact via a conductive bearing, e.g. asliding bearing, a rolling element type bearing, or other suitablebearing. The conductive bearing is located in a volume which is filledwith a substantially incompressible fluid to protect the bearing.

However, many modifications are possible without materially departingfrom the teachings of this disclosure. Accordingly, such modificationsare intended to be included within the scope of this disclosure asdefined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described withreference to the accompanying drawings, wherein like reference numeralsdenote like elements. It should be understood, however, that theaccompanying figures illustrate the various implementations describedherein and are not meant to limit the scope of various technologiesdescribed herein, and:

FIG. 1 is a schematic illustration of an example of a system havingcomponents which undergo relative rotation with respect to each other,according to an embodiment of the disclosure;

FIG. 2 is a cross-sectional view of an example of an electrical couplerwhich couples components which undergo relative rotation with respect toeach other, according to an embodiment of the disclosure;

FIG. 3 is a cross-sectional view of another example of an electricalcoupler which couples components which undergo relative rotation withrespect to each other, according to an embodiment of the disclosure;

FIG. 4 is a cross-sectional view of another example of an electricalcoupler which couples components which undergo relative rotation withrespect to each other, according to an embodiment of the disclosure; and

FIG. 5 is a cross-sectional view of another example of an electricalcoupler which couples components which undergo relative rotation withrespect to each other, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of some embodiments of the present disclosure. However,it will be understood by those of ordinary skill in the art that thesystem and/or methodology may be practiced without these details andthat numerous variations or modifications from the described embodimentsmay be possible.

The present disclosure generally relates to a system and methodology forfacilitating communication of electrical signals between componentswhich rotate relative to each other. The system and methodology forcommunicating electrical signals are useful in a variety of harshenvironments, e.g wellbore environments. In many applications, thetechnique comprises rotatably and electrically coupling a firstcomponent with a second component. For example, the first component maybe electrically coupled with the second component via an electricalcoupler. The electrical coupler utilizes a first electrical contactconductively connected with a second electrical contact via a conductivebearing. By way of example, the conductive bearing may be in the form ofa plain bearing, e.g. sliding bearing, or a rolling-type bearing, e.g. acylindrical roller bearing or a ball bearing. The conductive bearing islocated in a volume which is filled with a substantially incompressiblefluid to protect the bearing.

The electrical coupling utilizes a pressure permeable housing incombination with the conductive bearing, e.g. a rolling bearing. In someapplications, the rolling bearing may comprise a ball bearing in theform of a shielded or sealed ball bearing unit. The pressure permeablehousing may be packed with grease or another suitable fluid that issubstantially incompressible. The grease or other fluid may be de-gassedto further reduce its compressibility. The bearing is protected againstoverheating via operation at a relatively slow speed and/or via flow ofcooling fluid past the bearing. In certain wellbore applications, forexample, a cooling flow of fluid may be directed past the electricalcoupling to remove heat generated by the bearing. In drillingapplications, a flow of drilling mud may be used to provide the cooling.

In some embodiments, the bearing can be used to perform a dual duty ofproviding both a conductive path between components undergoing relativerotation and as a bearing to facilitate the relative rotation. Theelectrical coupler may be constructed to provide a sealed electricalpath through the races of the bearing, thus allowing electrical signalsto be passed between the components. In some applications, theelectrical signals are passed between a rotatable shaft and an adjacenthousing via conductive, rolling contact elements of a bearing placedbetween the rotatable shaft and the adjacent housing.

Referring generally to FIG. 1, an example of a system 20, e.g. a wellsystem, is illustrated as having a first component 22 which is rotatablewith respect to a second component 24. Electrical signals routed along aconductor 26, e.g. an electrical communication line, pass between thefirst component 22 and the second component 24 via an electrical coupler28. By way of example, the electrical signals may be sent to ortransmitted from an electrical device 30.

In the specific example illustrated, system 20 is in the form of a wellsystem comprising a well string 32, e.g. a tubing string, extendingalong a wellbore 34 from a wellhead, a drilling rig, or other suitablesurface equipment 36. In some applications, one of the components 22, 24is stationary while the other is rotatable. For example, first component22 may be stationary with respect to the portions of well string 32above component 22 while the second component 24 is rotatable withrespect to first component 22. However, the components 22, 24 may berotated at different speeds relative to a third reference and/or theymay be rotated at the same speed during certain periods of operation.The rotatable second component 24 may comprise a shaft or a variety ofother types of rotatable components. It should be noted the electricalcoupler 28 also may be used in a variety of surface or non-well relatedapplications to facilitate transmission of electrical signals betweencomponents that undergo relative rotation with respect to each other.

Referring generally to FIG. 2, an example of the electrical coupler 28is illustrated. In this example, the electrical coupler 28 comprises ahousing 38 which may be part of or attached to first component 22. Thehousing 38 is engaged with second component 24 in a manner which allowsrelative rotation between the housing 38/first component 22 and thesecond component 24. By way of example, the second component 24 maycomprise a rotatable shaft 40 which rotates about an axis 42. Theelectrical coupling 28 further comprises an electrical contact 44positioned at the first component and another electrical contact 46positioned at the second component. Additionally, a bearing 48 ismounted between the first component 22 and the second component 24, e.g.between housing 38 and shaft 40. The bearing 48 may comprise a varietyof sliding-type bearings or rolling-type bearings, e.g. ball bearings,cylindrical roller bearings, or rolling pin bearings. The bearing 48also is formed of a conductive material, e.g. a conductive steelmaterial, to enable efficient transfer of electrical signals betweenelectrical contacts 44 and 46.

In the example illustrated, bearing 48 comprises a first race 50 mountedagainst first component 22 and in contact with first electrical contact44. The bearing 48 also comprises a second race 52 mounted againstsecond component 22 and in contact with second electrical contact 46.The electrical contacts 44, 46 are otherwise insulated but conductivelyconnected to the races 50, 52, respectively, so that an electricalsignal may pass through bearing 48. The bearing 48 further comprises aplurality of rotatable members 54 which are rotatably trapped betweenthe first race 50 and the second race 52.

In an embodiment, bearing 48 is in the form of a plain bearing havingsliding contact surfaces which may be lubricated. In other embodiments,bearing 48 may be in the form of a rolling-type bearing having rollingcontact elements in the form of rotatable members 54. By way of example,rotatable members 54 may be cylindrical rollers, balls, pins, or othersuitable rotatable members. Additionally, bearing 48 may be in the formof a shielded or sealed unit bearing. The bearing 48 also may beelectrically isolated via insulating material or insulating devices sothat short circuits do not occur. In some applications, the bearingraces 50, 52 or other bearing components may be formed partially ofplastic or other materials and provided with conductive contacts tomaintain the electrical connection during relative rotation of firstcomponent 22 with respect to second component 24.

As illustrated in FIG. 2, the bearing 48 is located in a cavity 56disposed between the first component 22 and the second component 24. Byway of example, the cavity 56 may be formed in housing 38 and may extendto second component 24. The cavity 56 has a volume for receiving asubstantially incompressible fluid 58 which surrounds at least a portionof the bearing 48. In a variety of applications, the substantiallyincompressible fluid 58 may be in the form of grease. Additionally, thesubstantially incompressible fluid 58 may be de-gassed to further reduceits compressibility.

The electrical coupler 28 also is constructed to enable pressureequalization between the cavity 56 and an exterior region 60 outside ofcavity 56 and housing 38. According to an embodiment, the pressureequalization may be achieved through a porous material 62. The porousmaterial 62 may be in the form of a porous gland/membrane 64 placedbetween the first component 22, e.g. the stationary component, and thesecond component 24, e.g. the rotary component.

By making provision for a volume around the bearing 48 that is filledwith nearly incompressible fluid 58, e.g. grease, fluid that enterscavity 56 is effectively isolated from the bearing 48. At most, minutevolumes of external fluid can enter the cavity 56 before the pressuresare equalized. Once equilibrium is achieved, there is no mechanism tofurther drive the exterior fluid into bearing 48. The porous gland 64may further be used to filter out abrasive particles from external fluidwhich enters cavity 56. The porous gland 64 also blocks fluid flow whichcould potentially remove the grease or other incompressible fluid 58from cavity 56.

The porous gland/membrane 64 also may be originally filled with a cleanand neutral fluid 66, e.g. oil or grease, such that minute amounts ofthis clean and neutral fluid 66 are displaced into cavity 56 duringpressure equalization. The clean and neutral fluid 66 may have a volumegreater than the change in volume of the fluid 58 in cavity 56 whenplaced under hydrostatic compression resulting from the incomingexternal fluid that drives the clean fluid 66 from the pores of porousmaterial 62. Undesirable, external borehole fluid is thus maintained inexternal region 60 outside of cavity 56. In some applications, theporous gland 64 may be in the form of a felt material, and the cleanfluid 66 may be in the form of a grease impregnating the felt material.However, various other porous materials 62 may be used to constructporous gland 64 including sponge materials, porous metals, porouscomposites, and/or other suitably porous materials. Similarly, a varietyof greases, viscous liquids, and other suitable fluid and materialmixtures may be used for fluids 58 and 66. Depending on the application,fluid 66 and fluid 58 may be of the same type of fluid or of differenttypes of fluid.

If the volume of grease or other substantially incompressible fluid 58is large enough, a “stirring” effect resulting from rotation of thebearing 48 does not reach the outer zones of cavity 56. The size ofcavity 56 may thus be used to further limit the ability of externalfluid to migrate to the bearing 48 if minute amounts of such externalfluid move into the outer reaches of cavity 56. By using shielded orsealed bearings 48, the mechanical stirring effect can further bereduced or eliminated, thus providing additional protection againstparticles in the substantially incompressible fluid 58. The shielded orsealed bearings 48 also are filled with grease or another suitablefluid. In some applications, the shielded or sealed bearings 48 may bein the form of standard shielded or sealed bearings.

Referring generally to FIG. 3, another embodiment of the electricalcoupler 28 is illustrated. In this embodiment, housing 38 is a poroushousing formed at least in part of porous material 62. It should benoted, however, the porous material 62 used to form housing 38 may be adifferent type of material than the porous material used to form porousgland/membrane 64. For example, the porous gland 64 may be a softmaterial, e.g. felt, and the porous material 62 used to form poroushousing 38 may be a harder material which retains its form. Examples ofharder, porous material comprise a porous metallic material, porousceramic material, or porous composite material. A specific example of amaterial comprises (Mite® Bearing material available from BeemerPrecision, Inc.

In the example illustrated, the pores of porous housing 38 may bepre-loaded with clean fluid 66. The clean fluid 66 may be a suitablegrease, oil, or other material. Considerable volumes of clean fluid 66may be held in the porous material of housing 38 for the purpose ofpressure compensation. The large areas exposed to pressure allow thehousing 38 to transmit balancing fluid more quickly and to thus supportquicker pressure compensation. A variety of seals 68, e.g. conventionalshaft seals, may be disposed between the first component 22 and secondcomponent 24, as illustrated. The structure illustrated in FIG. 3facilitates operation of the system with considerable pressure gradientsacting across the bearing 48. As with the previous embodiment, thebearing 48 may be electrically isolated so that electrical signals canpass between electrical contacts 44, 46 without creating ashort-circuit.

In another embodiment, housing 38 is a solid housing and seals 68 areused between first component 22 and second component 24, as illustratedin FIG. 4. However, a porous element 70 is located in housing 38 andextends through housing 38 between cavity 56 and exterior region 60. Theporous element 70 is formed with a suitable porous material 62 so as tofacilitate pressure equalization. As with previous embodiments, thepores of porous material 62 may be filled with clean fluid 66. Theporous element 70 is sized properly so as to act as a clean fluidreservoir while remaining sealed at the interface with the surroundingportions of housing 38.

In another embodiment illustrated in FIG. 5, housing 38 is again a solidhousing and seals 68 are used between first component 22 and secondcomponent 24. However, the porous element 70 is located in secondcomponent 24 and extends through the second component 24 between cavity56 and exterior region 60. By way of example, the second component 24may be in the form of shaft 40 and porous element 70 may be routed alongshaft 40 for exposure to both cavity 56 and exterior region 60. In someapplications, the entire shaft 40 may be formed from porous material 62so as to facilitate a greater rate of pressure equalization. In thislatter embodiment, the pores of porous material 62 also may be filledwith clean fluid 60. In some applications, both first component 22 andsecond component 24 (or portions of each of the components 22, 24) maybe formed of a suitable porous material 62.

Depending on the application, system 20 may have a variety ofconfigurations comprising other and/or additional components. Forexample, the shape and structure of the components 22 and 24 may vary insize and configuration depending on the parameters of a givenapplication and environment. Similarly, a variety of materials may beused to construct the various components of the electrical coupler 28.The system 20 also may utilize many types of electrical devices 30 forvarious downhole applications or other types of applications. Thebearing 48 may comprise a variety of plain bearings having conductivesliding contact surfaces or a variety of roller-type bearings havingconductive rolling members, e.g. cylinders, balls, pins, or othersuitable, conductive rolling contact elements.

Although a few embodiments of the disclosure have been described indetail above, those of ordinary skill in the art will readily appreciatethat many modifications are possible without materially departing fromthe teachings of this disclosure. Accordingly, such modifications areintended to be included within the scope of this disclosure as definedin the claims.

What is claimed is:
 1. A system for use in a well, comprising: a wellstring having a first component, a second component, and an electricalcoupler for conducting electric current between the first component andthe second component, the first component being rotatable with respectto the second component, the electrical coupler comprising: a firstelectrical contact positioned in the first component; a secondelectrical contact positioned in the second component; a bearing formedof conductive material and mounted between the first component and thesecond component, the bearing being formed of a ii conductive materialand being located in a cavity between the first component and the secondcomponent; and a substantially incompressible fluid disposed in thecavity.
 2. The system as recited in claim 1, wherein pressure equalizesbetween the cavity and an exterior region outside of the cavity.
 3. Thesystem as recited in claim 2, wherein the substantially incompressiblefluid comprises a grease.
 4. The system as recited in claim 3, whereinthe first component comprises a shaft.
 5. The system as recited in claim4, wherein the bearing comprises a first race mounted against the firstcomponent in contact with the first electrical contact, a second racemounted against the second component in contact with the secondelectrical contact; and a plurality of conductive contact elementsrotatably trapped s between the first race and the second race.
 6. Thesystem as recited in claim 2, wherein the pressure equalizes through aporous gland material placed between the first component and the secondcomponent.
 7. The system as recited in claim 6, wherein the porous glandmaterial contains a fluid.
 8. The system as recited in claim 2, whereinthe pressure equalizes through a porous material located in at least oneof the first component or the second component.
 9. The system as recitedin claim 2, wherein the second component is formed of a porous materialand further wherein the pressure equalizes through the porous material.10. The system as recited in claim 2, wherein the first component isformed of a porous material and further wherein the pressure equalizesthrough the porous material.
 11. A method, comprising: rotatablymounting a first component with respect to a second component; locatinga first electrical contact at the first component and a secondelectrical contact at the second component; conductively connecting thefirst electrical contact and the second electrical contact via aconductive bearing; and filling a volume around at least a portion ofthe conductive bearing with a substantially incompressible fluid. 12.The method as recited in claim 11, wherein rotatably mounting comprisesrotatably mounting first and second well components.
 13. The method asrecited in claim 12, wherein conductively connecting comprisesconnecting via the conductive bearing by engaging a first race of theconductive bearing with the first component, engaging a second race ofthe conductive bearing with the second component, and rotatablycapturing a plurality of the conductive rotatable members between thefirst race and the second race such that electricity may be conductedthrough the first race, the plurality of conductive rotatable members,and the second race.
 14. The method as recited in claim 13, whereinfilling the volume comprises filling the volume with a grease.
 15. Themethod as recited in claim 13, further comprising equalizing pressurebetween an exterior region and the volume via a porous material.
 16. Themethod as recited in claim 15, further comprising using the porousmaterial to prevent movement of particulates into the volume.
 17. Themethod as recited in claim 12, further comprising moving the firstcomponent and the second component downhole into a wellbore and removingheat generated by the ball bearing via flow of a well fluid.
 18. Asystem for communicating electrical signals, comprising: a firstcomponent rotatably mounted with respect to a second component; a firstelectrical contact located at the first component and a secondelectrical contact located at the second component, the first electricalcontact being operatively coupled with the second electrical contact viaa conductive bearing, the conductive bearing having a plurality ofrotatable members which rotate during rotation of the first componentwith respect to the second component; and a housing creating a volumearound at least a portion of the conductive bearing, the volume beingfilled with a substantially incompressible fluid.
 19. The system asrecited in claim 18, wherein the first component and the secondcomponent are downhole well components.
 20. The method as recited inclaim 18, wherein the conductive bearing comprises a first race engagedwith the first component, a second race engaged with the secondcomponent, wherein the plurality of rotatable members are rotatablytrapped between the first race and the second race such that electricitymay be conducted through the first race, the plurality of rotatablemembers, and the second race.